Electric Compressor and Air Conditioning System for vehicle, Using the Electric Compressor

ABSTRACT

An electric compressor ( 20 ) comprises an electric motor ( 70 ) enclosed in a motor casing ( 33 ), a division wall ( 60 ) dividing the interior of the motor casing ( 33 ) and having an inner side surface in contact with a working fluid before compressed, a leg ( 120 ) integrally formed on an outer side surface of the division wall ( 60 ), and a control board ( 111 ) with a microcomputer ( 112 ) for driving the electric motor ( 70 ) mounted, the control board being fixed to the leg ( 120 ).

TECHNICAL FIELD

This invention relates to an electric compressor and an automotive airconditioning system, and particularly an electric compressor suited foran automotive air conditioning system.

BACKGROUND ART

Electric compressors have a compression unit and an electric motorenclosed in a housing. Some electric compressors have also an invertercircuit for driving the electric motor and a control circuit forcontrolling the inverter circuit, within the housing.

These circuits, particularly the inverter circuit tends to become highin temperature while supplying electric power to the electric motor.Thus, the circuit board of the inverter circuit is arranged in alow-temperature region within the housing. For example, the electriccompressor disclosed in Japanese Unexamined Patent Publication No.2003-139069 has a circuit board of an inverter circuit fixed in closecontact with a division wall of the housing, where the division wall iscooled by a working fluid before compressed by the compression unit.

In addition, the electric compressor disclosed in the above publicationhas a temperature sensor attached to the circuit board. When thetemperature detected rises above an upper limit, the rotation speed ofthe motor is increased to increase the flow rate of the working fluid,thereby cooling the circuit sufficiently. Thus, in this electriccompressor, the electric components constituting the circuit areexpected to be prevented from overheating, which results in an increasein durability of the circuit, and therefore of the compressor.

DISCLOSURE OF THE INVENTION

The primary object of this invention is to provide an electriccompressor which is further increased in reliability of preventing theoverheating of the electric components and therefore has a furtherincreased durability, and an automotive air conditioning system usingthe electric compressor.

In order to achieve the above object, an electric compressor accordingto the present invention comprises an electric motor for driving acompression unit for compressing a working fluid, enclosed in a housingtogether with the compression unit; a division wall dividing theinterior of the housing and having an inner side surface in contact witha working fluid before compressed by the compression unit; a legintegrally formed on an outer side surface of the division wall; and afirst circuit board on which electric components for driving theelectric motor are mounted, the first circuit board being fixed to theleg.

In the electric compressor according to the present invention, thecircuit board is fixed to the leg integrally formed on the divisionwall. Since heat is efficiently transferred between the circuit boardand the division wall via the leg, the circuit board has an increasedheat radiation performance. Consequently, the electric componentsmounted on the circuit board are reliably prevented from overheating andtherefore have an increased durability, which leads to an increaseddurability of the compressor.

Desirably, at least one of the electric components mounted on thecircuit board is in contact with said outer side surface. Desirably, theelectric compressor further comprises a second circuit board on whichelectric components for driving the electric motor in cooperation withthe electric components on the first circuit board are mounted, where atleast one of the electric components on the second circuit board is incontact with said outer side surface. In these desirable configurationsof the electric compressor, the electric component in direct contactwith the outer side surface of the division wall has an increased heatradiation performance. This prevents the overheating of this electriccomponent and therefore increases the durability of this electriccomponent, which leads to an increased durability of the compressor.

Desirably, a distal end of the leg is in contact with a metal part ofthe circuit board. In this desirable configuration of the electriccompressor, the contact between the distal end of the leg and the metalpart of the control board allows efficient heat transfer between the legand the circuit board, so that the circuit board has a further increasedheat radiation performance. This increases the reliability of preventingthe overheating of the electric components mounted on the circuit board.

Desirably, the metal part is a ground terminal of the circuit board. Inthis desirable configuration of the electric compressor, the contactbetween the distal end of the leg and the ground terminal allows heatproduced in the circuit board to be efficiently transferred to the legvia ground wiring provided to extend across the entire circuit board.Further, since the electric components mounted on the circuit board areconnected with the ground wiring, heat produced in the electriccomponents is also efficiently transferred to the leg via the groundwiring. This further increases the reliability of preventing theoverheating of the electric components mounted on the circuit board.

Desirably, the electric compressor further comprises a temperaturesensor fixed to one or each of the first and second circuit boards and acontrol means for driving the electric motor basing on a result ofdetection by the temperature sensor. In this desirable configuration ofthe electric compressor, the temperature of an electric component isdetected by the temperature sensor, and the control means drives theelectric motor basing on a result of detection by the temperaturesensor. The electric motor drives the compression unit, so that alow-pressure working fluid is drawn to the compression unit across thehousing. In this process, the division wall is cooled by the flowingworking fluid, so that the electric components are prevented fromoverheating.

Desirably, it is arranged such that when, in a waiting state of theelectric compressor, temperature detected by the temperature sensorrises above an activation temperature, the control means temporarilydrives the electric motor. In this desirable configuration of theelectric compressor, when in a waiting state of the electric compressor,temperature detected by the temperature sensor rises above an activationtemperature, the electric motor is temporarily driven. The electricmotor drives the compression unit, so that a low-pressure working fluidis drawn to the compression unit across the housing. Thus, also in thewaiting state of the electric motor, the division wall is cooled by theflowing working fluid, so that the electric components are preventedfrom overheating.

Here, the waiting state means a state in which an electric compressor,incorporated in a system to allow the system to perform a specificfunction, does not need to operate since the system is not performingthat function. For example, for an electric compressor used in anautomotive air conditioning system, the waiting state is a state inwhich cooling or dehumidifying the vehicle interior is not required.

Desirably, it is arranged such that when, in the waiting state of theelectric compressor, the temperature detected by the temperature sensordrops to or below a stop temperature, the control means stops thetemporarily-driven electric motor. In this desirable configuration ofthe electric compressor, when in the waiting state of the electriccompressor, the temperature detected by the temperature sensor drops toor below a stop temperature, the temporarily-driven electric motor isstopped. This allows the compressor to prevent the overheating of theelectric components, keeping energy consumption at a low level.

In order to achieve the above-mentioned object, an automotive airconditioning system according to the present invention has an electriccompressor in any of the above-described configurations, disposed in anengine room.

In the automotive air conditioning system according to the presentinvention, the electric compressor has an increased durability, whichresults in an increase in durability of the whole system.

Let us consider the case in which the automotive air conditioning systemis arranged such that when, in the waiting state of the electriccompressor, the temperature detected by the temperature sensor risesabove the activation temperature, the control means of the electriccompressor temporarily drives the electric motor. In this particularconfiguration, for example, even if the automotive air conditioningsystem is not performing a cooling or a dehumidification function whilethe engine is operating, when the engine room becomes hot so that thetemperature detected by the temperature sensor exceeds the activationtemperature, the electric motor is driven. Thus, the automotive airconditioning system arranged this way is increased in reliability ofpreventing the overheating of the electric components of the electriccompressor, which leads to a further increase in durability of the wholesystem.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a schematic configuration of an embodimentof an automotive air conditioning system;

FIG. 2 is a diagram showing a vertical cross section of an electriccompressor applied to the system shown in FIG. 1;

FIG. 3 is a diagram showing a part near the distal end of a leg in thecross section shown in FIG. 2, on an enlarged scale;

FIG. 4 is a diagram schematically showing wire connections between anelectric compressor, a battery and an air conditioning control device ofthe system shown in FIG. 1;

FIG. 5 is a flow chart schematically showing a protective operationprogram, which is executed by a control circuit shown in FIG. 4;

FIG. 6 is a diagram showing a part near a circuit chamber of a variantof the compressor; and

FIG. 7 is a flow chart schematically showing a variant of the protectiveoperation program, which is executed by the air conditioning controldevice shown in FIG. 4 as an interruption routine.

BEST MODE OF CARRYING OUT THE INVENTION

FIG. 1 shows a schematic configuration of an embodiment of an automotiveair conditioning system.

The system includes a refrigeration circuit 10, and a refrigerantcirculation passage 11 of the refrigeration circuit 10 extends from avehicle engine room 12 into a vehicle interior 14 through a partitionwall 13. Within the engine room 12, an electric compressor 20, acondenser 21, a receiver 22 and an expansion valve 23 are disposed inthe refrigerant circulation passage 11 in this order as viewed in thedirection of the refrigerant circulation. The electric compressor 20 isarranged near the engine 24, and the condenser 21 is arranged near avehicle radiator grill, together with a fan (not shown).

Within the vehicle interior 14, an evaporator 25 is disposed in therefrigerant circulation passage 11. The evaporator 25 is locateddownstream of the expansion valve 23. A front part of the vehicleinterior 14 is defined as an instrument room 27 by an instrument panel26, and the evaporator 25, enclosed in an air-conditioning unit housing28 together with a blower (not shown), is arranged within the instrumentroom 27.

FIG. 2 shows an electric scroll compressor used as the compressor 20.The compressor 20 has an approximately cylindrical housing 30, and thehousing 30 has a unit casing 31, a support wall 32 and a motor casing 33which are made of metal and arranged in this order, from the right tothe left in FIG. 2.

The unit casing 31 is in the shape of a cup, and a scroll unit 40 isenclosed in the unit casing 31. The scroll unit 40 has a fixed scroll 41and a movable scroll 42, and the fixed scroll 41 is fixed to an end wallof the unit casing 31 by a plurality of fixing bolts 43.

The interior of the unit casing 31 is axially divided in two by a baseplate of the fixed scroll 41, and a discharge chamber 44 is definedbetween the base plate of the fixed scroll 41 and the end wall of theunit casing 31. A discharge port 45 communicating with the dischargechamber 44 is formed in the cylindrical wall of the unit casing 31, at aposition near the end wall of the unit casing 31. The discharge port 45is connected to the condenser 21 by a segment of refrigerant circulationpassage 11.

The movable scroll 42 is arranged to the motor casing 33 side, and thefixed and movable scrolls 42, 42 are engaged such that a plurality ofcompression chambers 46 are formed between their spiral walls. As themovable scroll 42 moves circularly relative to the fixed scroll 41, thechambers 46 shift toward the center of the fixed and movable scrolls 41,42, reducing their volumes. The compression chamber 46 that has arrivedat the center communicates with the discharge chamber 44 via a dischargehole 47 formed approximately at the center of the base plate of thefixed scroll 41. The discharge hole 47 is opened and closed by adischarge valve (not shown). The discharge valve is a reed valveattached to the end face of the fixed scroll 41 which faces thedischarge chamber 44. Reference sign 48 indicates a valve holddownmember which regulates the opening of the reed valve.

Within the unit casing 31, there is defined an intake chamber 49surrounding the movable scroll 42. The compression chamber 46 that is atthe radially outermost position communicates with the intake chamber 49.

A support wall 32 is fitted to the open end of the unit casing 31. Thesupport wall 32 has a shaft hole in the center, and a communication hole34 outside the shaft hole. A rotary shaft 50 is passed through the shafthole, and a ball bearing 51 is fitted between the shaft hole and therotary shaft 50. The rotary shaft 50 has a large-diameter end portion 52positioned within the unit housing 31. On a crank pin 53 projecting fromthe large-diameter end portion 52, an eccentric bush 54 is fitted. Theeccentric bush 54 is enclosed in a boss 55 formed on the rear side ofthe movable scroll 42, and a needle bearing 56 is fitted between theeccentric bush 54 and the boss 55. By these crank pin 53, eccentric bush54 and needle bearing 56, rotation of the rotary shaft 50 is translatedinto circular motion of the movable scroll 42.

Between the base plate of the movable scroll 42 and the support wall 32,a ball coupling 57 is provided. The ball coupling 57 not only preventsthe movable scroll 42 from rotating on its axis while moving circularlyrelative to the fixed scroll 41, but also functions as a thrust bearingto receive reaction force against compression from the movable scroll42.

A motor casing 33 is in the shape of a cylinder open at either end. Themotor casing 33 and the unit casing 31 are connected by a plurality ofconnecting bolts 58, with the support wall 32 interposed between theiropen ends.

The interior of the motor casing 31 is axially divided in two by adivision wall 60. A stator chamber 61 is defined between the divisionwall 60 and the support wall 32. An intake port 62 communicating withthe stator chamber 61 is formed in the cylindrical wall of the motorcasing 33, at a position near the division wall 60. The intake port 62is connected to the evaporator 25 by a segment of refrigerantcirculation passage 11.

The above-mentioned rotary shaft 50 extends across the stator chamber61, and the end of the rotary shaft 50 opposite the large-diameter endis located near the division wall 60. A cylindrical bearing supportprojects from the center of the division wall 60, and a ball bearing 63is fitted between the inner surface of the bearing support and therotary shaft 50. Thus, the rotary shaft 50 is rotatably supported by theball bearings 51, 63 in a pair.

The rotary shaft 50 constitutes a part of a rotor 71 of, for example abrushless three-phase induction motor 70. A laminated member 72constituted by annular magnetic steel sheets, serving as anapproximately cylindrical iron core, is fitted on the rotary shaft 50.The laminated member 72 is held between end plates 73 in a pair at theopposite ends. The end plates 73 are connected by a plurality of rivets74.

The laminated member 72 of the rotor 71 is surrounded by a stator 80,and the stator 80 includes an approximately cylindrical core 81. Thecore 81 is fitted into the inner cylindrical surface of the motor casing33 and fixed to the division wall 60 by fixing bolts 82. A plurality ofslots are formed in the inner cylindrical surface of the core 81,circumferentially apart from each other, so that stator teeth areprovided between the adjacent slots. Wire is wound around each statortooth to form coils 83. By supplying a current to the coils 83, eachstator tooth is magnetized.

The laminated member 72 of the rotor 71 and the stator 70 are locatedapproximately in the middle in the axial direction of the stator chamber61, and the division wall 60 side and the support wall 32 side of thestator chamber 61 communicate with each other, for example through a gap(not shown) provided between the laminated member 72 and the stator 80.Thus, the intake port 62 communicates with the intake chamber 49 via thestator chamber 61.

From the coils 83 of the stator 80, three input lines (not shown)extend, and the ends of the three input lines are connected to ends ofthree pins 90 extending through the division wall 60 in an air-tight andinsulated manner, respectively. Only one of the three pins 90 is shownin FIG. 1.

The other ends of the three pins 90 located within a circuit chamber 91function as an input of the electric motor 70, namely, U-, V- andW-terminals. The circuit chamber 91 is defined between the division wall60 and an end plate 92 fixed at the end of the motor casing 33 oppositethe support wall.

An output of an inverter circuit 100 disposed in the circuit chamber 91is electrically connected to the above-mentioned ends of the pin 90,namely, the U-, V-, and W-terminals. The inverter circuit 100 is athree-phase bridge circuit, and includes a printed circuit board 101(hereinafter referred to as an “inverter board”) and an IGBT module 102mounted on the inverter board 101.

The inverter board 101 is arranged near and parallel to the divisionwall 60 and screwed to the division wall 60. The IGBT module 102 islocated between the inverter board 101 and the division wall 60, and theupper surface of the IGBT module 102 is in direct plane contact with thedivision wall 60. When viewed in the circumferential direction of themotor casing 33, the IGBT module 102 is in contact with the divisionwall 60 at the position approximately corresponding to the intake port62.

An input of the inverter circuit 100 is electrically connected to abattery 109 (DC power source) disposed in the engine room 12, via aninput/output plug 108 attached to the cylindrical wall of the motorcasing 33. The input of the inverter circuit 100 is also electricallyconnected to an output of a control circuit 110, which is also disposedin the circuit chamber 91.

The control circuit 110 is provided to perform VVVF control(variable-voltage variable-frequency control) on the inverter circuit100, and includes a printed circuit board 111 (hereinafter referred toas a “control board”) and electric components, such as a microcomputer112 and a capacitor 113, mounted on the control board 111.

The control board 111 is larger than the inverter board 101, and locatedfurther from the division wall 60 than the inverter board 101 is. Thecontrol board 111 is supported by a plurality of columnar legs 120. Eachleg 120 integrally projects from the division wall 60, and when viewedin the axial direction of the motor casing 33, the distal ends of allthe legs 120 are on the same imaginary plane. Since the circuit chamber91 side surface of the division wall 60 is not flat, the legs 120 aredifferent in length.

As shown in FIG. 3, bottomed threaded holes 121 open at the centers ofthe distal ends of the legs 120, respectively. The control board 111 hasthrough holes 122 at the positions corresponding to the threaded holes121. Each of the through holes 122 has its open ends in metal lands 123,124 formed on each side of the control board 111. The inner surface ofthe through hole 122 is covered with a metal coating 125, and the metalcoating 125 connects the lands 123, 124.

Each through hole 122 extends through a metal layer 126 provided withinthe control board 111 for grounding, and the metal coating 125 and themetal layer 126 are joined. When the control board 111 is fixed to thelegs 120 by fastening screws 127 into the threaded holes 121 via thethrough holes 122, the distal ends of the legs 120 and the heads of thescrews 127 come in direct plane contact with the corresponding lands123, 124, respectively.

Referring back to FIG. 2, an input of the control circuit 110 isconnected to an air conditioning control device 130 via theabove-mentioned input/output plug 108. The air conditioning controldevice 130 is placed in the above-mentioned instrument room 27.

This electric compressor 20 further includes temperature protectioncircuits for the inverter circuit 100 and the control circuit 110,respectively, and the temperature protection circuits include atemperature sensor 150 mounted on the inverter board 101 and atemperature sensor 151 mounted on the control board 111, respectively.The temperature sensor 150 on the inverter board 101 is arranged nearthe IGBT module 102 to detect the temperature of the IGBT module 102,and the temperature sensor 151 on the control board 111 is arranged nearthe microcomputer 112 to detect the temperature of the microcomputer112. The temperature sensors 150, 151 are electrically connected to theinput of the control circuit 110.

The circuit chamber 91 is filled with a resin material to protect theinverter circuit 100, the control circuit 110 and the temperatureprotection circuits against vibration, although hatching for indicatingthe resin material is omitted in FIG. 2.

FIG. 4 schematically shows wire connections between the above-describedelectric motor 70, inverter circuit 100, control circuit 110, airconditioning control device 130, temperature protection circuits andbattery 109.

As seen from FIG. 4, the IGBT module 102 includes six IGBTs(insulated-gate bipolar transistors) 160, which are power transistors,six feedback diodes 161 and a smoothing capacitor 162. The controlcircuit 110 switches a gate voltage to the gate terminal of each IGBT160 on and off.

Next, the operation of the above-described automotive air conditioningsystem will be described.

The air conditioning control device 130 performs main control over theautomotive air conditioning system. When the vehicle interior 14 needsto be cooled or dehumidified according to an instruction given by apassenger, the air conditioning control device sends a control signal tothe control circuit 110 of the electric compressor 20. Receiving thecontrol signal, the control circuit 110 applies a gate voltage to theIGBTs 160 of the inverter circuit 100, thereby driving the electricmotor 70. As the electric motor 70 operates, the rotary shaft 50rotates, which causes the movable scroll 42 to move circularly. Thecircular movement of the movable scroll 42 results in shift of thecompression chambers 46.

As the compression chambers 46 shift, an intake step, namely a step oftaking a refrigerant, or a working fluid from the intake chamber 49 intothe compression chambers 46, a compression step, namely a step ofcompressing the taken-in refrigerant in the compression chambers 46, anda discharge step, namely a step of discharging the compressedrefrigerant from the compression chambers 46 into the discharge chamber44 are performed. In other words, the refrigerant in gas form in theevaporator 25 is drawn to the intake port 62 via the refrigerantcirculation passage 11, and the refrigerant in high-temperature liquidform is sent from the discharge port 45 to the condenser 21 via therefrigerant circulation passage 11.

Here, the gaseous refrigerant in the evaporator 25 results from almostcomplete vaporization of the refrigerant exiting the expansion valve 23in a wet state. An air current created by a blower to flow across theexterior of the evaporator 25 is cooled by the refrigerant taking heatto vaporize. The resulting cold air is heated as necessary, and thencaused to flow into the vehicle interior 14, so that the vehicleinterior 14 is cooled or dehumidified.

In addition to the above-described main control performed by the airconditioning control device 130, the microcomputer 112 of the controlcircuit 110 constantly executes a temperature protection program shownin FIG. 5. It is to be noted that the microcomputer 112 executes twotemperature protection programs provided for the IGBT module 102 and themicrocomputer 112, in parallel. Since these two temperature protectionprograms are almost the same in structure, the temperature protectionprogram for the microcomputer 112 will be described as an example.

According to the temperature protection program, first whether or notthe control circuit 110 is requested by the air conditioning controldevice 130 to activate the compressor 20, namely whether or not thecontrol circuit 110 has received from the air conditioning controldevice 130 a control signal indicating that the compressor 20 should beactivated (S10). As long as the air conditioning control device 130requests activation of the compressor 20, step S10 of the program isrepeated. If the air conditioning control device 130 does not requestactivation of the compressor 20, the control circuit 110 determineswhether or not the compressor 110 is in operation (S20).

If at step S20, it is determined that the compressor 20 is at rest,whether or not the temperature Tm of the microcomputer 112 detected bythe temperature sensor 150 is higher than a predetermined activationtemperature T2 is determined (S30). The activation temperature T2 is 85°C., for example. If the temperature Tm is not higher than the activationtemperature T2, the flow of control returns to step S10. If thetemperature Tm is higher than the activation temperature T2, the controlcircuit 110 applies a gate voltage to each of the IGBTs 160 atpredetermined timings, thereby driving the electric motor 70, therebyactivating the compressor 20 (S40).

After the compressor 20 is activated, the control circuit 110 determineswhether or not the temperature Tm is lower than a predetermined stoptemperature T1 (S50). The stop temperature T1 is lower than theactivation temperature T2, and 80° C., for example. If the temperatureTm is lower than the stop temperature T1, the control circuit 110 ceasesto apply the gate voltage to each of the IGBTs 160, thereby stopping theelectric motor 70, thereby stopping the compressor 20 (S60). If thetemperature Tm is not lower than the stop temperature T1, the flow ofcontrol returns to step S10. If the air conditioning control device 130does not request the activation of the compressor 20 when the flow ofcontrol has returned to step S10, it means that the compressors 20 hasbeen activated at step S40 in a preceding cycle. Thus, the flow ofcontrol jumps to step S50 from step S20.

The schematic structure of the temperature protection program for themicrocomputer 112 is as described above. In the temperature protectionprogram for the IGBT module 102, the temperature Tm in the temperatureprotection program for the microcomputer 112 is replaced with thetemperature Ti of the IGBT module 102 measured by the temperature sensor150.

In the above-described embodiment of the automotive air conditioningsystem, the electric compressor 20 has an increased durability comparedwith the compressor in the conventional system, which results in anincreased durability of the whole system. The reasons for the increasein durability of the electric compressor 20 are as follows:

In the electric compressor 20, the control board 111, disposed fartherfrom the division wall 60 than the inverter board 101, is fixed to thedistal ends of the legs 120 integrally formed on the division wall 60.Since heat is efficiently transferred between the control board 111 andthe division wall 60 via the legs 120, the control board 111 has anincreased heat radiation performance. Consequently, the electriccomponents mounted on the control board 111 to constitute the controlcircuit 110, such as the microcomputer 112 and the capacitor 113, arereliably prevented from overheating, which results in an increase indurability of the electric components constituting the control circuit110, and therefore of the compressor 20.

Further, in the electric compressor 20, the IGBT module 102 mounted onthe inverter board 101 is in direct contact with the circuit chamber 91side surface of the division wall 60, so that the IGBT module 102 has anincreased heat radiation performance. Thus, the IGBT module 102, or inother words, the electric components constituting the inverter circuit100, such as the IGBTs 160, the feedback diodes 161 and the smoothingcapacitor 162, are prevented from overheating and therefore have anincreased durability, which results in an increase in durability of thecompressor 20.

Further, in the electric compressor 20, the distal end of each leg 120is in contact with the metal land 123 on the control board 111, whichallows efficient heat transfer between the legs 120 and the controlboard 111, so that the control board 111 has a further increased heatradiation performance. This increases the reliability of preventing theoverheating of the electric components constituting the control circuit110.

Further, in the electric compressor 20, each land 123 is joined to themetal layer 126 provided for grounding the control circuit 110 andfunctions as a ground terminal. The contact between the distal ends ofthe legs 120 and the lands 123 allows heat produced in the control board111 to be efficiently transferred to the legs 120 via the metal layer126 provided to extend across the entire control board 111 in apredetermined pattern. Particularly, since the metal layer 126 isconnected to the respective electric components constituting the controlcircuit 110, heat produced in the electric components is alsoefficiently transferred to the legs 120 via the metal layer 126. Thisfurther increases the reliability of preventing the overheating of theelectric components constituting the control circuit 110.

Further, the temperatures Ti, Tm of the IGBT module 102 and themicrocomputer 102 are detected by the temperature sensors 150, 151,respectively, and the electric compressor 20 is activated by themicrocomputer 112 of the control circuit 110 on the basis of thedetection results. Specifically, even in a waiting state in which theelectric compressor 20 is not requested to operate by the airconditioning control device 130, if at least one of the temperatures Ti,Tm detected by the temperature sensors 150, 151 rises above theactivation temperature T2, the electric compressor 20 is temporarilyactivated by the microcomputer 112 of the control circuit 110. When theelectric compressor 20 is activated, the electric motor 70 drives thescroll unit 40, i.e., the compression unit, so that a low-pressurerefrigerant is drawn to the compression unit across the stator chamber61. Thus, also in the waiting state, the division wall 60 is cooled bythe flowing refrigerant, so that the electric components, including theIGBT module 102 and the microcomputer 112, are prevented fromoverheating.

Further, if, in the waiting state, the temperatures Ti, Tm detected bythe temperature sensors 150, 151 drop to or below the stop temperatureT1, the electric compressor 20 is stopped by the microcomputer 112 ofthe control circuit 110. This allows the electric compressor 20 toprevent the overheating of the electric components, keeping powerconsumption at a low level.

Specifically, in the automotive air conditioning system using thiselectric compressor 20, for example when the operation of the engine 24makes the engine room 12 hot so that the temperatures Ti, Tm detected bythe temperature sensors 150, 151 exceed the activation temperature T2,the electric compressor 20 in the waiting state is temporarilyactivated. Thus, in this system, the electric components used in theelectric compressor 20 are prevented from overheating with an increasedreliability, which results in a further increase in durability of thewhole system.

The present invention is not limited to the above-described embodimentbut can be modified in various ways. For example, although in thedescribed embodiment, the inverter circuit 100, the control circuit 110and the temperature protection circuits are disposed in the circuitchamber 91, another circuit can be disposed therein.

Further, the number of circuit boards disposed therein is not limited totwo, namely the inverter board 101 and the control board 111. Forexample, as shown in FIG. 6, the inverter circuit, the control circuitand the protection circuits can be constructed on a single circuit board155.

Although in the described embodiment, the control board 111 is fixed tothe distal ends of the legs 120, the number of legs 120 can be reducedup to one. The shape as well as the size of the leg is not limited to aparticular one. The leg can be in the shape of a circular column, anelliptic column, a rectangular column, a circular truncated cone or thelike. In an example where a single circuit board is fixed to four legsin the shape of a circular column, the legs measure no less than 5 mmbut no greater than 30 mm in length and no less than 10 mm but nogreater than 14 mm in diameter, for example.

Although in the described embodiment, the inverter circuit isconstructed using an IGBT module, the inverter circuit can use powertransistors other than IGBTs as switching devices.

Although in the described embodiment, two temperature sensors 150, 151are arranged to measure the temperatures Ti, Tm of the IGBT module 102and the microcomputer 112, the temperature sensors can be arranged tomeasure the temperatures of other electric components. Further, thenumber of temperature sensors provided is not limited to two.

Although in the described embodiment, the electric motor 70 of theelectric compressor 20 is a brushless induction motor, the structure ofthe electric motor provided is not limited to a particular one. Further,although in the described embodiment, the electric compressor 20 is anelectric scroll compressor having a compression unit constituted by ascroll unit 40, the electric compressor can be an electric reciprocatingcompressor having a compression unit constituted by a cylinder block anda piston.

Although in the described embodiment, the microcomputer 112 of thecontrol circuit executes a protective operation program, it can bearranged such that the air conditioning control device 130 providedoutside the compressor 20 executes a protective operation program, forexample as an interrupt routine, in addition to programs for maincontrol. In this case, the temperature sensors 150, 151 are connected tothe air conditioning control device 130 as indicated in broken lines inFIG. 4. As seen from FIG. 7, the protective operation program executedby the air conditioning control device 130 is slightly different fromthe flow chart shown in FIG. 5. Specifically, it differs in that the airconditioning control device 130 determines whether or not it isrequested, in the main control, that the control circuit 110 shouldactivate the compressor 20 (S10′), requests the control circuit 110 toactivate the compressor 20 (S40′), and requests the control circuit 110to stop the compressor 20 (S60′).

Last, it goes without saying that the electric compressor according tothe present invention is applicable to systems other than the automotiveair conditioning system.

1. An electric compressor, comprising: an electric motor for driving acompression unit for compressing a working fluid, enclosed in a housingtogether with the compression unit, a division wall dividing theinterior of the housing and having an inner side surface in contact witha working fluid before compressed by the compression unit, a legintegrally formed on an outer side surface of the division wall, and afirst circuit board on which electric components for driving theelectric motor are mounted, the first circuit board being fixed to theleg.
 2. The electric compressor according to claim 1, wherein at leastone of said electric components mounted on the circuit board is incontact with said outer side surface.
 3. The electric compressoraccording to claim 1, wherein a distal end of the leg is in contact witha metal part of the circuit board.
 4. The electric compressor accordingto claim 3, wherein the metal part is a ground terminal of the circuitboard.
 5. The electric compressor according to claim 2, wherein a distalend of the leg is in contact with a metal part of the circuit board. 6.The electric compressor according to claim 5, wherein the metal part isa ground terminal of the circuit board.
 7. The electric compressoraccording to claim 1, further comprising: a temperature sensor fixed tothe circuit board, and a control means for driving the electric motorbasing on a result of detection by the temperature sensor.
 8. Theelectric compressor according to claim 7, wherein when, in a waitingstate of the electric compressor, temperature detected by thetemperature sensor rises above an activation temperature, the controlmeans temporarily drives the electric motor.
 9. The electric compressoraccording to claim 8, wherein when, in the waiting state of the electriccompressor, the temperature detected by the temperature sensor drops toor below a stop temperature, the control means stops thetemporarily-driven electric motor.
 10. The electric compressor accordingto claim 1, further comprising a second circuit board on which electriccomponents for driving the electric motor in cooperation with saidelectric components on the first circuit board are mounted, wherein atleast one of the electric components on the second circuit board is incontact with said outer side surface.
 11. An automotive air conditioningsystem comprising an electric compressor disposed in an engine room,said electric compressor comprising: an electric motor for driving acompression unit for compressing a working fluid, enclosed in a housingtogether with the compression unit, a division wall dividing theinterior of the housing and having an inner side surface in contact witha working fluid before compressed by the compression unit, a legintegrally formed on an outer side surface of the division wall, and afirst circuit board on which electric components for driving theelectric motor are mounted, the first circuit board being fixed to theleg.
 12. The automotive air conditioning system according to claim 11,wherein at least one of said electric components mounted on the circuitboard is in contact with said outer side surface.
 13. The automotive airconditioning system according to claim 11, wherein a distal end of theleg is in contact with a metal part of the circuit board.
 14. Theautomotive air conditioning system according to claim 13, wherein themetal part is a ground terminal of the circuit board.
 15. The automotiveair conditioning system according to claim 12, wherein a distal end ofthe leg is in contact with a metal part of the circuit board.
 16. Theautomotive air conditioning system according to claim 15, wherein themetal part is a ground terminal of the circuit board.
 17. The automotiveair conditioning system according to claim 11, wherein the electriccompressor further comprises: a temperature sensor fixed to the circuitboard, and a control means for driving the electric motor basing on aresult of detection by the temperature sensor.
 18. The automotive airconditioning system according to claim 17, wherein when, in a waitingstate of the electric compressor, temperature detected by thetemperature sensor rises above an activation temperature, the controlmeans temporarily drives the electric motor.
 19. The automotive airconditioning system electric compressor according to claim 18, whereinwhen, in the waiting state of the electric compressor, the temperaturedetected by the temperature sensor drops to or below a stop temperature,the control means stops the temporarily-driven electric motor.
 20. Theautomotive air conditioning system according to claim 11, wherein theelectric compressor further comprises a second circuit board on whichelectric components for driving the electric motor in cooperation withsaid electric components on the first circuit board are mounted, and atleast one of the electric components on the second circuit board is incontact with said outer side surface.